In the context of the present patent:                “spraying” refers to the use of pulverized (atomized) liquid mixtures;        the term “articles” is understood as meaning both finished products and components and semi-finished articles used to produce finished products;        “thin”, both in the case of articles and in the case of coatings, refers to a thickness which may be even less than one millimeter and in practice is between 0.1 and 4 mm;        “high definition” refers to the possibility of reproducing very fine designs or textures.        
The conventional techniques for producing articles using basic components consisting of reactive polymer materials in the form of very viscous fluids as well as any auxiliary filler materials such as coloured pigments, flame retardants, etc., employ devices such as those described, for example, in the U.S. Pat. No. 3,035,775. In this device the basic components are thoroughly mixed together and pressurized air is added to the resultant reaction product (polymer mixture) so that it can be sprayed through an end nozzle.
These techniques are undoubtedly satisfactory, as demonstrated by their widespread use, but they have a number of important limitations with regard to the production of thin articles or coatings with very small and well-defined designs. In this case it is required to use spraying devices which ensure very small flowrates and which therefore have an end nozzle with a very small cross-section. A nozzle of this kind, however, becomes blocked very rapidly owing to the viscosity and reactivity of the basic components of the polymer mixture.
The device described in the U.S. Pat. No. 4,778,659 (corresponding to EP 0,209,888) comprises a splined shaft which is rotated at a speed of between 100 and 3200 rpm so as to receive sequentially and mix two reactive polymer liquids. The device comprises an outlet opening with substantially the same diameter as the shaft, through which the resultant reaction product, i.e. the polymer mixture, is discharged without being pulverized (atomized), and therefore this device is not a spraying device.